Pump assembly



March 9, 1965 v. P. M. BALLU 3,172,369

PUMP ASSEMBLY Filed March 29, 1962 3 Sheets-Sheet 1 IAWENTOQ ArroliuevsMarch 9, 1965 y. P. M. BALLU 3, 7 ,3

PUMP ASSEMBLY Filed March 29, 1962 3 Sheets-Sheet 2 lwemox March 9, 1965v. P. M. BALLU PUMP ASSEMBLY 3 Sheets-Sheet 3 Filed March 29, 1962United States Patent 1 Claims. (31. 103-175 This invention relates topumping assemblies of a type that has come into use of recent yearsespecially in the pumping of abrasive, corrosive and other deleteriousfluids, and wherein a double-acting reciprocating piston assemblyoperates to pump the fluid from an inlet to an outlet of the pump casingby the creation of oppositely, cyclically, varying pressures in a pairof opposed pumping chambers, the ends of the double-acting pistonassembly serving, on reciprocation of the assembly, to vary thepressures in said chambers by way of scaled deformable diaphragms sothat no part of the rnOVing mechanism of the pump will at any time beexposed to the flow of deleterious fluid being pumped.

The objects of this invention relate to the solution of a number ofpractical difliculties that have been found to arise in the constructionand operation of such pumps. Thus, objects of the invention are toprovide an improved construction of the sealed, double-actingreciprocatory piston assembly, whereby its construction will besimplified, driving efliciency improved, efiicient lubricationfacilitated. Another object is to improve the design and mounting of theflexible diaphragms used in such a pump. A further object lies in theprovision, in association with a pump of the above character, of gaspressure accumulator means serving to reduce fluctuations in outletfluid pressure over the pumping cycle. Other objects relate to thegeneral construction of the pump assembly and its various componentsincluding the inlet and outlet valve means used therein, wherebymanufacture and assembly are facilitated and made more economical,ruggedness and service life are improved, and dismantling and remountingoperations are facilitated to expedite inspection and repairs. Otherobjects may appear from the detailed description to follow.

An exemplary embodiment of the invention will now be described forpurposes of illustration but not of limitation with reference to theaccompanying drawings, which are more or less simplified for purposes ofclarity, and wherein:

FIG. 1 is an outer plan View of an improved doubleacting pump assemblyaccording to the invention.

FIG. 2 is a side elevational view of the pump assembly, as seen from theleft hand end of the assembly shown in FIG. 1.

FIG. 3 is a vertical section, with parts shown in elevation, and as seengenerally on the line indicated by III III in FIG. 1.

FIG. 4 is a vertical section, with parts in elevation, generally on thebroken line lV-IV indicated in FIG. 1 as regards the upper part of FIG.4, and along an axial plane of the reciprocatory assembly as regards thelower part of said figure.

FIG. 5 is a fragmentary sectional view on an enlarged scale illustratingpart of a flexible diaphragm according to a preferred feature of theinvention, and

FIG. 6 is a separate view, on an enlarged scale, showing a modified formof the double-acting reciprocatory piston assembly, with the left sideof the figure shown in section and the right half in outer elevation.

Referring to FIGS. 1 to 4, the improved pump structure comprises acasing 1 defining an inner cavity 2 having opposite aligned sideopenings providing bearing 3,172,369 Patented Mar. 9, 1965 surfaces 3aand 3b. The cavity 2 further has a top opening 4 provided with a sealingplug 5 which may be made of suitable plastic material. Bodily movable asa unit in sealing relationship with the side bearing surfaces 311 and 3bare a pair of similar pistons 6a and 611 having flat outer faces mergingover rounded surfaces with the cylindrical side surfaces of saidpistons. Both pistons are rigidly interconnected into a unitarystructure by means of a spacer sleeve 11 having its opposite endspress-fitted around respective cylindrical bosses 7a and 7b projectinginwards from the inner end faces of the pistons 6a and 6b. Seated withinthe sleeve 11 and spaced inwardly from the side walls of it is anactuator bush 8 formed with a bore 9 in central relation with thepistons and sleeve, and having its end faces seated against the innerends of bosses 7a and 7b. The end faces of bush 8 are formed withlubricating grooves 8a and 8b. Openings 12 formed through the top andbottom of the sleeve 11 permit the free circulation of oil filling thecavity 2 for an efficient lubrication of the mechanism therein.

The sleeve 11 is further formed with aligned openings 13 and 14 throughits sides (see FIG. 3) through which extends an eccentric intermediateportion 16 of a drive shaft 15 serving to reciprocate the piston unit.The shaft 15 is formed beyond the ends of the intermediate eccentricpart 16 with journal portions of larger and smaller diameter than theintermediate portion, which journal portions are rotatably mounted inrespective bearing sleeves 17 and 18 positioned in apertured bosses 19and 20 respectively formed in the corresponding sides of the casing 1.Annular seals 21 and 22 serve to seal said apertures around the shaftjournals. The boss 20 housing the larger-diameter journal of shaft 15 isformed as a flange having holes 23 in it for securing the pump casing tosupporting structure as with bolts. The end of shaft 15 projectingbeyond said flange outwardly of the casing is shown provided with aslotted type of coupling sleeve 24 for connection to a suitable motornot shown.

A pair of strong, flexible, cup-shaped diaphragms 25a, 25b, have theirrim flange portions 26a, 26b securely attached to the opposite ends ofcasing 1 around the piston bearing surfaces 3a, 3b in rebates 27a, 27bformed on the casing. The diaphragms 25a, 25b are arranged to have theirintermediate wall portions in engagement with the flat outer faces ofpistons 6a, 6b.

The structure so far described including the casing 1 is partlysurrounded by an outer casing structure including a pair of shellmembers 28a, 2812 having tapered flanges 29a, 29]) at the bottomthereof, adapted to engage around the lower rebates 27a, 2% so as tocontribute to retaining the diaphragms 25a, 25b in position thereon. Forassembling the shell members 28a, 28b around the inner casing there areprovided e.g. four tie-bolts 311 which extend through apertured lugs 31of the shell members and through recesses 32 in the inner casing. Inoperation a film of oil is present between the outer faces of pistons6a, 6b and the inner surfaces of the diaphragms 25a, 25b. To completethe outer casing structure there is provided a domed cover 40 fittedover the flat top surfaces of the shell members 28a, 28b and assembledthereon by means of bolts 54-.

Formed in each of the shell members 28a, 28b is an inlet channel 33 andan outlet channel 34 separated by a partition Web 35 visible in FIG. 4,left. Both channels in each shell member communicate at their lower endswith the variable-pressure chamber in which the related diaphragm 251:or 25b is movable. The upper end of the inlet channel 33 in each shellmember communicates with I a related one of two inlet valves such as thevalve 36 shown at the right of FIG. 4, while the upper end of the outletchannel 34 in each shell member connects with a Q a related one of twooutlet valves such as the valve 37 shown at the left of FIG. 4. As willbe seen from this figure, the inlet valves 36 are housed in recesses 38provided in the related shell member at the upper end of the inletchannel 33, while the outlet valves 37 are housed in recesses 39. formedin the pump cover 46. Each of the four valves includes a valve seatmember 36a or 37a respectively and an overlying perforate cup member 36bor 37b in which is movably positioned a vlve member 360 or 37c biassedagainst the valve seat by a spring 36d or 37d.

Overlying the inner casing 1, between the shell members 28a and 28b, isa pressure accumulator 41 having the form of a two-part reservoirincluding a lower body element 41 and an upper cover element 53 betweenwhich a flexible diaphragm 43 is clamped. The under side of element 52is formed with a concavity or depression facing the inner casing. Thediaphragm 43 is in the form of a generally flat cup-like member similarto the diaphragms 25a and 25b, and has its outer rim flange engaged in arebate 44 formed in the under surface of the cover element 53, while theedge flange of the body element 41 is formed with another rebate 45 ofrounded contour to participate in clamping the rim of the diaphragmunder the action of bolts 46 (see FIGS. 1 to 3). An inflating air valve42 (FIGS. 1 and 2) extends outwardly from the body 41 of the pressureaccumulator and permits the pumping into the cavity beneath diaphragm 43of the body of air or other gas under high pressure to inflate thediaphragm for a purpose later described.

FIG. illustrates an advantageous construction of the diaphragm 43 whichmay also be used in connection with the diaphragms 25a and 25b earlierdescribed. As shown, the rim flange of the diaphragm 43 is formed withan outer peripheral circumferential groove 43b and an innercircumferential groove 43a. The walls of each groove lie at an acuteangle to each other with the apex inclined towards the outer end of thediaphragm so as to form circumferential lips 43c providing an extremelytight seal.

The pump cover 40 above the cover element 53 of the pressure accumulatordefines a pair of parallel spaced passages 48, 49 separated by apartition web 47 (see especially FIG. 3). Passage 48 is an inlet passageand terminates at each of its ends, on each side of the pump assembly,just above the related one of the two inlet valves 36. Similarly passage49 is the outlet passage of the pump and terminates at each end justabove the related one of the two outlet valves 37. Further, intakepassage 48 at substantially its midpoint communicates with an inletopening 5t) formed in the pump cover 40, while outlet passage 49 atitsmidpoint communicates with an outlet opening 51 formed in the pump cover40 next the inlet opening. In addition, the outlet passage 49communicates through a port 52 with the upper chamber in the pressureaccumulator defined above diaphragm 43.

In the operation of the pump system described, it will be understoodthat the system actually performs as two separate pumps both taking influid from the common inlet 50 and both discharging into the commonoutlet 51. More specifically, on the shaft being driven in rotation froma motor not shown, the eccentric 16 acting on the actuator member 8imparts reciprocation to the dual piston structure 6a-6b. Consideringone side of the dual pump system, say the right side in FIG. 4, as thepiston 6b covered by sealing diaphragm b recedes leftward to theretracted position shown, liquid is drawn in from inlet 50 through inletpassage 48 past the right hand inlet valve 36 and through the intakechannel 33 into the variable-volume chamber adjacent diaphragm 251) onthe right hand side of the pump. Then as the piston 6b advancesrightward on continued rotation of shaft 15, the liquid thus drawn intothe said chamber is discharged by the outgoing piston through theright-hand outlet channel 34, past the right-hand outlet valve (notshown, but

similar to the left-hand outlet valve 37), and into the outlet passage49 and out through the outlet 51.

The operation on the left hand side of the pump system is identical tothat just described, but occurs with a phase displacement as will bereadily understood.

The function of the pressure accumulator 41 is to impart continuity tothe pumping operation by averaging out the pressure differences over thepumping cycle. More precisely, as the liquid under pressure is beingdischarged through outlet passage 49 to the outlet 51, its pressure isapplied by way of port 52 tothe air-inflated diaphragm 43, and since thegas below the diaphragm is compressible whereas the liquid above thediaphragm is not, the diaphragm yields elastically, compressing the bodyof gas beneath it. In the next half of the cycle when no liquid is beingdischarged under pressure from the piston through outlet passage 49, thecompressed body of gas expands and gives up the pressure accumulated init, through diaphragm 43, to the liquid; Thus a substantiallycontinuous, pulse-free discharge outflow of liquid is obtained from thepump.

In the modified piston structure shown in F166, the sleeve 54 whichcorresponds in function to sleeve 11 in the first embodiment described,comprises a length of sheet metal tubing formed with perforations 55 forthe free circulation of lubricating oil and holes 56 through which thedrive shaft extends. Thesleeve54 is pressfitted at its ends around thebosses 57 'of the respective piston members 58. The piston members aredesirably made from a light alloy. In each boss 57 there is formed aperipheral groove 59 into' which the sleeve 11 is crimped or swaged asshown at 60. The actuator member 61 is formed with the central bore 62surrounding the eccentric portion of the drive shaft and has its ends 63seated against thin-gauge discs 64 of hardened steel lining the innerfaces of the piston members for reducing wear. After assembly of theparts just described, a cup-like capping member 65 is injection-moldedover each end of the assembly from a suitable plastic material such as apolyamide (nylon). Preferably a circumferential gap 66 is providedbetween the larger-diameter part of the piston 58 and the adjacent endof sleeve 54, into which the plastic flows during the injection moldingstep to improve the bond.

The construction just described provides a substantial saving in weightand reduces machining operations, since the only parts of the structurerequiring tobemachined to close tolerances are the cylindrical pistonsurfaces around which the sleeve ends are fitted and the flat surfaceson which the actuator vmember applies its thrust. The actuator member 61preferably made of suitable antifriction metal operates in engagementwith the hard steel surfaces of the insert discs 64, and the moldedplastic caps 65 provide an excellent seal both Withthe casing bearingsurfaces 3a, 3b and the diaphragms such as 25a, 25b. The provision ofthe plastic caps molded over the piston members eliminates closemachining tolerances, since the depth of plastic liable to dimensionalvariations is small as compared to piston diameter.

It will be understood that various modifications may be made in thestructural details illustrated and described without exceeding the scopeof the invention.-

What I claim is:

1. A pumping system comprising in combinationz an inner casing formedwith opposite axially aligned cylinders; a pair of opposite pistonsrespectively mounted for reciprocation in said cylinders, said pistonshaving cylindrical bosses projecting toward each other; a driver memberprovided with a bOre perpendicular to the! axis of said cylinders andslidably mounted between said bosses; a spacer sleeve, provided withholes registering with said bore and rigidly secured onto said bossesfor interconnecting said pistons coaxially; a driving shaft mounted forrotation across said casing and passing through said holes and throughsaid bore, said shaft being provided with an eccentric section engagingsaid bore; a pair of cup-shaped flexible diaphragms externally fittedonto the ends of said cylinders and engaging the outer faces of saidpistons respectively; shell members fitted to said casing around saiddiaphragms for clamping said diaphragm around said cylinders anddefining variable pressure chambers on each side of said casing; anouter casing provided with a fluid inlet and outlet and fitted to saidshell members and valve means interposed between said outer casing andsaid shell members for connecting said chambers to said fluid inlet andoutlet, whereby a fluid may be pumped by the system on actuation of saiddriving shaft.

2. The combination of claim 1 wherein said outer casing is provided witha depression facing said inner casing and with a port allowing acommunication between said depression and said fluid outlet; aprotruding circular edge surrounding said depression, a cup-shapedflexible diaphragm engaged onto said edge, a cup-shaped rigid memberengaged onto said diaphragm and adapted for clamping it on said edgewhen said outer casing is fitted to said shell members; and valve meansfor introducing a gas under pressure between said diaphragm and saidrigid member.

3. The combination of claim 2 wherein said inner casing is provided withan aperture facing said outer casing; an obturating member for saidaperture, said obturating member abutting onto said cup-shaped rigidmember when said outer casing is fitted onto said shell members.

4. The combination of claim 2 wherein said cup-shaped flexiblediaphragms are provided with circumferential sealing grooves.

5. The combination of claim 1 wherein said spacer sleeve has endspress-fitted around said bosses, capshaped plastic coatings being moldedover the outer surface of said pistons and an adjacent part of the endsof said spacer sleeve.

6. The combination of claim 5 wherein said pistons are provided withperipheral grooves for improving the bond between said pistons, saidspacer sleeve and said cap-shaped coatings.

7. The combination of claim 5 wherein said pistons and said drivermember are made out of a light metal alloy, resistant insert discs beinginterposed between said pistons and said driver member.

Rererences Cited by the Examiner UNITED STATES PATENTS 1,658,850 2/28Mars 103-175 2,076,732 4/37 Kuehne 103-175 2,083,073 6/37 Loeber 103175FOREIGN PATENTS 336,671 1/04 France. 599,933 3/48 Great Britain.

ROBERT M. WALKER, Primary Examiner.

LAWRENCE V. EFNER, Examiner.

1. A PUMPING SYSTEM COMPRISING IN COMBINATION: AN INNER CASING FORMEDWITH OPPOSITE AXIALLY ALIGNED CYLINDERS; A PAIR OF OPPOSITE PISTONSRESPECTIVELY MOUNTED FOR RECIPROCATION IN SAID CYLINDERS, SAID PISTONSHAVING CYLINDRICAL BOSSES PROJECTING TOWARD EACH OTHER; A DRIVER MEMBERPROVIDED WITH A BORE PREPENDICULAR TO THE AXIS OF SAID CYLINDERS ANDSLIDABLY MOUNTED BETWEEN SAID BOSSES; A SPACER SLEEVE, PROVIDED WITHHOLES REGISTERING WITH SAID BORE AND RIGIDLY SECURED ONTO SAID BOSSESFOR INTERCONNECTING SAID PISTON COAXIALLY; A DRIVING SHAFT MOUNTED FORROTATION ACROSS SAID CASING AND PASSING THROUGH SAID HOLES AND THROUGHSAID BORE, SAID SHAFT BEING PROVIDED WITH AN ECCENTRIC SECTION ENGAGINGSAID BORE; A PAIR OF CUP-SHAPED FLEXIBLE DIAPHRAGMS EXTERNALLY FITTEDONTO THE ENDS OF SAID CYLINDERS AND ENGAGING THE OUTER FACES OF SAIDPISTONS RESPECTIVELY; SHELL MEMBERS FITTED TO